Variable Speed Limit Control for Delay and Crash Reductions at Freeway Work Zone Area

Improving operational efficiency and safety on freeway segments has long been recognized as a priority in traffic communities. This study presents a comprehensive variable speed limit (VSL) control model for reducing both travel delays and potential crash risks at freeway work zones. The proposed strategy offers the responsible agency a reliable way to determine reasonable speed limits over the control time horizon in response to traffic fluctuations. The control objective of the proposed system is to minimize total operational cost by using embedded functions to estimate total cost with total travel delay and potential crash rate on the targeted freeway segment. This study used a field site in China for its case study to evaluate the effectiveness of the proposed VSL control system. Based on the experimental results, it was observed that the proposed control model shows promise in reducing average delay, number of stops, and average stopped delay on the studied freeway segment. In addition, simulation experiments for sensitivity analysis indicate that the proposed VSL control model is more effective when driver compliance rate exceeds a threshold of 60% and the user-defined benefit threshold ranges 10—20%.